Signal device for producing sound in telephone instruments



Nov. l7, 1959 B. v. MYRGREN ETA!- 2,913,715

SIGNAL DEVICE FOR PRODUCING souun IN TELEPHONE INSTRUMENTS Filed Oct, 14, 1957 Z'IVVENTORS x R RN Mm 0 r M a R mm KEMH V a r G M 5 SIGNAL DEVICE non PRODUCING SOUND IN TELEPHONE INSTRUMENTS Bengt Viktor Myrgren, Hagersten, and Leif Branden, Enskede, Sweden, assignors to Telefonaktiebolaget L M Encsson, Stockholm, Sweden, a corporation of Sweden The present invention refers to a signal device for producing sound in telephone instruments in which the sound producing member comprises an oscillating diskshaped armature influenced by an alternating electromagnetic field.

Earlier known signal devices of this kind are often difficult to regulate and adjust; moreover they are generally expensive to manufacture and require a relatively large space within the instrument. The purpose of the present invention is to provide a signal device in which these inconveniences are substantially eliminated.

The arrangement according to the invention is mainly characterized by an electromagnet the magnetic material of which envelops the core and winding of the magnet and has an opening in the axial direction of the core. The electromagnet further has an armature in the form of a disk disposed in front of the opening of the envelope. A spring between the disk and the envelope yieldably holds the disk a predetermined distance from the envelope. A regulating member is also provided to facilitate the adjustment of the compression of the spring and the amplitude of the oscillation.

The invention will be more fully explained with reference to the attached drawing in which:

Fig. 1 is a longitudinal sectional view through a device made in accordance with the invention, and

Fig. 2 is a top plan view of the device shown in Fig. 1, the armature being removed.

A cylindrical envelope having an opening at one end and made of magnetic material, such as soft iron, is provided with a concentric iron core 2. In the space between the core 2 and the envelope 1 a magnetic coil 3 is positioned. An armature 4 in the form of a round disk is positioned in front of the opening of the envelope in such a way that it is pressed outwardly by a spring washer 5 against a screw head. The washer is supported by the envelope at its periphery and is cut out so that inwardly extending springy arms are formed, which press with their ends against the disk. The spring washer 5 has at its periphery a plurality of projections 8, each of which engages a notch 9 in the wall of the envelope. Due to such suspension, the armature will oscillate in the axial direction of the iron core when an alternating current flows through coil 3. By means of the screw 6 the air gap and thus the amplitude may be adjusted and the sensitivity and the volume of sound can be changed.

As the armature when oscillating may strike against the envelope and/ or against the core, a variation of the volume of sound and its pitch may be obtained.

In order to obtain a maximum value of sound the armature must strike against the envelope as strongly as possible and must return into its initial or rest position as fast as possible. This is obtained by correlating the length and direction of the projections 8 in relation to the arms 10 so that, when the arms 10 are depressed by the downward moving armature 4, the outermost parts of the projections are rocked in upward direction in the notches of the envelope beyond the end of the envelope ice thus engaging the downward moving armature 4. This provides additional spring tension which urges the armature back into the rest position when the armature is no longer attracted by the field into downward direction. This additional spring tension does not materially reduce the velocity of the armature, since the arms 10 may be rather weak and the additional spring tension becomes only effective when the armature has obtained a high velocity at which time the air gap is very small so that the magnetic field is almost at maximum strength.

The compact design of the signal device facilitates the mounting of the same, which for instance may be done by means of a screw 7 carried by the bottom of the envelope.

The invention is, of course, not limited to the shown embodiment, different modifications being possible within the scope of the invention. The spring washer 5 may, for instance, be replaced by a cup spring.

We claim:

1. A signal device for producing sound in telephone instruments, said device comprising, in combination, a magnet having a core and an energizing coil, a casing of magnetic material surrounding said magnet and having one side opening axially of said magnet in one direction, a disc shaped armature supported in front of said open side of the casing and movable into striking engagement with an edge portion of said casing at said open end for producing sound in response to energization of said magnet, resilient means between said disc and said casing for damping said movement of said disc, and adjustable means normally maintaining said disc at a definite distance from said casing against the tension of said resilient means upon de-energization of said magnet.

2. A signal device for producing sound in telephone instruments, said device comprising a magnet having a core and an energizing coil, a cylindrical casing of magnetic material surrounding said magnet symmetrical with the axis of said core, one end of said casing defining an opening, a disc shaped armature supported in front of saidopening of said casing, and resilient means acting between said disc and said casing, said armature being movable against said resilient means into striking engagement with an edge portion defining said opening of said casing in response to energization of said magnet.

3. A signal device for producing sound in telephone instruments, said device comprising, in combination, a magnet having a core and an energizing coil, a casing of magnetic material surrounding said magnet and having one end defining an opening, a disc shaped armature supported in front of said one open end of said casing and movable into striking engagement with an edge portion of said casing at said open end, and resilient diaphragm means acting between said disc and said casing, said diaphragm means having a peripheral annular por tion and resilient arm-shaped extensions within said annular portion, said extensions projecting outwardly from the plane of the diaphragm into engagement with said disc shaped armature to damp the inward movement thereof.

4. A signal device as set forth in claim 3 wherein said arm shaped extensions extend radially inwardly from said annular portion and along the periphery of said core.

5. A signal device for producing sound in telephone instruments, said device comprising, in combination, a magnet having a core and an energizing coil, a casing of magnetic material surrounding said magnet and having one side opening axially of said magnet in one direction, a disc shaped armature supported in front of said open side of said casing and displaceable in response to energization of said magnet into striking engagement with an edge portion of said casing around said open side,

outwardly extending projections forming continuations of said inwardly directed projections and defining two-arm levers roekably engaging said annular portion of said casing, said outwardly directed projection being movable outwardly in response to inward movement of said inwardly directed projections by said disc.

References Cited in the file of this patent UNITED STATES PATENTS" 881,712 Pape Mar. 10, 1903 

